Electron discharge device anode



P 1953 R. c. SCOTT 2,653,259

ELECTRON DISCHARGE DEVICE ANODE Filed March 29, 1946 INVENTOR. ROBERT C.SCOTT BY v Wa QM.

ATTORNEY Patented Sept. 22, 1953 UNITED STATES PATENT OFFICE ELEc'rEoNDISCHARGE DEVICE ANODE Robert C. Scott, Belmont, Mass., assignor to theUnited States of America as represented by the Secretary of WarApplication March-29, 1946, Serial No. 657,947 3 Claims. (Cl. 313-31)This invention relates generally to electrical apparatus, and, moreparticularly to an anode for a high frequency thermionic vacuum tube,for example, of the resnatron type.

There have been devised various types of high frequency, high powervacuum tubes. The powerdissipated at the anode of such a tube isoften'considerable, and, hence some means of cooling, usually by air orwater, is necessary. A factor which limits the efficiency of many ofsuch tubes is secondary emission of electrons from the anode, especiallywhen the anode potential is near or below that of the screen grid. Byreducing the effect of secondary emission, the efficiency of operationis improved, and, hence, a smaller plate power dissipation is possiblefor a given power output, and the problem of anode cooling may berendered somewhat less complex.

It is, therefore, an object of the present invention to provide a highfrequency vacuum tube anode which will reduce the efiect of secondaryemission and thus improve the efliciency of operation of the vacuumtube.

It is another object to provide a means for cooling this anode.

The invention, in general, may be embodied in an annular metallic anodehaving on its inner surface a series of radial planar flanges, fins orplate-like members, and having an inner cavity through which water maybe circulated for cool- 8'.

Other objects, features and advantages of this invention will becomeapparent from the following description taken in connection with theaccompanying drawing in which:

Fig. 1 is a plan view of one embodiment of the invention; and

Fig. 2 is a cross-sectional view of the embodiment shown in Fig. 1,taken along line 2-2 thereof except that the cathode is not shown.

The embodiment of Fig. 1 is one which is adapted to be mounted betweenthe upper and lower sections of a high-frequency vacuum tube of a typewhich may be disassembled when not in operation. Such a tube may be ofthe resnatron type, for example such as is disclosed in the copendingapplication of John W. Livingood, Winfield W. Salisbury, and Edward S.Welch, issued as Patent No. 2,562,319 on July 31, 1951, Serial No.648,542, filed February 18, 1946. The resnatron has also been describedin the February 1946 issue of Electronics published by McGraw- HillPublishing Company, New York, New York. The main anode structurecomprises a metallic annulus ill to the inner annular surface of whichare aflixed a series of radial metallic fins I2. These fins may beattached by brazing or any other suitable means. At the center of thecircular aperture formed by the anode structure is a cathode 13. Asecond metallic annulus l4 having a circumferential flange It isarranged to fit closely around the outside of annulus i0, and may bejoined thereto by brazing or similar means. Flange It has a series ofholes 13 by means of which the entire structure may be fastened. betweenthe upper'and lower portions of the vacuum tube with which it is to beused.- Annulus i0 and annulus l4 have adjacent circumferentialindentations Z0 and 22 around their outer and inner peripheries,respectively. These indentations are of such dimensions that when theanode is assembled as shown in the drawing, an inner toroidal cavity 23is formed through which water may be circulated by means of inletconduit 24 and outlet conduit 26. These two conduits may be enclosedwithin the same envelope if desired. A partition 28 separates the inletand outlet sections of the cavity so that the cooling medium maycirculate freely therein.

A cross-sectional view of the anode along line 2-2 of Fig. 1 is shown inFig. 2, which indicates more clearly the cavity formed by indentations2B and 22 in annulus l0 and annulus I4 respectively. The cathode is notillustrated in Fig. 2.

The series of apertures or spaces 30 between radial fins l2 may beconsidered to be substantially equipotential cavities. The primaryelectrons from the cathode, which would ordinarily be located at or nearthe center of the circle formed by the anode as shown in Fig. 1, may beconsidered to give up their energy to the electric field at the timethey pass into the cavities. These primary electrons thus impinge on thesurface of the anode with rather low velocity. The problem of emissionof secondary electrons is thereby reduced, and those that are emittedtend to be arrested by the fins due to their low velocity, which is aresult of the low electrostatic field gradient within the cavity. Theloss of efficiency which would ordinarily be caused by this secondaryemission is thereby reduced. Other phases of the operation of theinvention will be obvious from the figures taken in conjunction with thedescription given above.

Although the embodiment described is adapted for use in a vacuum tubewhich may be disassembled, it will be obvious that the same structuremay be embodied in a vacuum tube of the ordinary permanently-sealedtype.

While there has been here described what is at 3 present considered tobe the preferred embodiment of the invention, it will be obvious tothose skilled in the art that various changes and modifications may bemade therein without departing from the scope of the invention.

The invention claimed is:

1. A vacuum tube .anode comprising an inner metallic annular section, anouter annular section adjacent and joined thereto, a plurality ofmetallic fins afiixed to the inner circumferential surface of said innerannular section and perpendicular thereto, said inner and enter annularsections bearing circumferential indentations on their adjacentsurfaces, said indentations jointly forming a toroidal cavity, and aninlet conduit and an outlet conduit communicating with said cavity.

2. A vacuum tube anode comprising a metallic annular portion having aninner circumferential surface for collecting primary electrons, saidsurface defining a cylindrical space, means producing an equipotentialregion adjacent said surface for reducing secondary electron emissiontherefrom, said means including a p'luurality of spaced metallic finsaffixed to said surface, said fins extending radially inwardly less thanone-half the distance to the center of said space with their ends spacedapart a substantially greater distance than their smallest physicaldimension, and a hollow annular chamber within the body of said annularportion for circulating a cooling medium.

3. In an electron tube, an anode comprising a body portion having aninner wall portion defining a central aperture, a cathode within saidaperture for emitting primary electrons toward said inner wall portion,and means for reducing secondary electron emission from said inner wallportion comprising a plurality of substantially planar metallic finportions aflixed to said inner wall portion and extending inwardlytoward said 'cathode less than one-half the distance to the center ofsaid aperture.

ROBERT C. SCOTT.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,628,999 Ronci May 17, 1927 2,380,502 Clarke et a1 July 31,1945 2,394,396 Mouromtseff et a1. Feb. 5, 1946 2,406,276 White Aug. 20,1946 2,412,772 Hansell Dec. .17, 1946 2,462,510 Korman Feb. 22, 19492,492,996 Haxby Jan. 3, .1950

FOREIGN PATENTS Number Country Date 509,102 Great Britain July '11, 1939

